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239A

 
    
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The 239A is a mechanically rigid version of the 215A (US) 4215A (UK) triode and was introduced in 1927.
See Wecovalve for the simpler style of construction.
The Etched lettering and Made in USA.
The UX4 solid base pins for fitting in the bayonet socket.
The triode section with side supports and glass bead.
A closer view of the anode and grid.
The single strand filament can just be seen.
The wide glass tube envelope is 25 mm in diameter, and excluding the UX4 base pins is 87 mm tall.
References: Datasheet, 1040 & 1043. Type 239A was first introduced in 1927.

 

Pin Connections
UX4
1
2
3
4
f
a
g1
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
μ
1.25
0.27
-1
Updated August 18, 2017.
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